Ответ:
Pascal?
var min, max, j, count: integer;
begin
min:=30000;
max:=0;
readln(j);
while j <> 0 do begin
if (j mod 5 = 0) and (j < min) then begin
min:= j;
count:= count + 1;
end;
if (j mod 5 = 0) and (j > max) then begin
max:= j;
count:= count + 1;
end;
readln(j);
end;
if count = 0 then write('NO') else write((min+max)/2);
end.